10 years ago by
A Pianist
When you say sore hand, it makes me think that you're using the soft flesh of your fingers to do the glissando. I remember the first time I saw the technique used like that, by someone on a keyboard with really light keys. I went home, tried it on my piano and sliced a layer of skin off!
The method I use most of the time is to use thumb nails when descending in right (ascending in left) and the nails of my second and third fingers when going the other way. It takes some care to ensure you don't hit the soft skin just above the nails though (ivory doesn't look to good with a bright red stripe down the middle!).
I have also used the palm of my hand if I want both black and white keys - you see Hammond organ players doing this fairly frequently.
It seems that if you want just black keys you might need to use the soft side of your fingers.
I've never managed an octave glissando - I saw Paul Lewis do one in a Beethoven piano concerto once - it looked like he had fingers of steel.
I hope some of this is useful.